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Texas Instruments SN74LS644-1N3
- Part No.:
- SN74LS644-1N3
- Manufacturer:
- Texas Instruments
- Package:
- 20-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74LS644-1N3.pdf
- Description:
- IC TXRX INVERT 5.25V 20DIP
- Quantity:
- Payment:
- Shipping:
Inventory:6,450
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Product details
Overview
SN74LS644-1N3 from Texas Instruments is an octal bus transceiver with open-collector outputs, designed for asynchronous bidirectional data transfer between two 8-bit buses in TTL systems. It features direction control (DIR), active-low output enable (G\), and supports 5-V operation with IOL rated to 48 mA per output. Used in legacy industrial backplane interfaces and parallel bus isolation circuits.
For engineers reviewing the SN74LS644-1N3 datasheet, SN74LS644-1N3 pinout, SN74LS644-1N3 application, or SN74LS644-1N3 equivalent, key selection criteria include open-collector drive capability, -1 version current rating, DIR/G\ logic polarity, and compatibility with LS-family timing and voltage thresholds.
Technical Context
This device implements dual 8-bit bidirectional data paths controlled by a single DIR input: when DIR = HIGH, data flows A→B; when DIR = LOW, data flows B→A. The G\ input disables all outputs into high-impedance state, enabling bus sharing without contention.
Open-collector outputs require external pull-up resistors and support wired-AND logic, level translation, and mixed-voltage interfacing. The -1 suffix denotes enhanced sink current capability (48 mA vs. standard 24 mA), critical for driving multiple TTL inputs or LEDs directly.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - Ensures stable operation across standard TTL supply tolerances. |
| IOL (per output) | 48 mA - Supports direct drive of up to 10 standard TTL loads or indicator LEDs without buffering. |
| Propagation Delay | 20 ns max (A-to-B or B-to-A) - Compatible with 25-MHz bus clocking in synchronous designs. |
| Input Threshold | VIL ≤ 0.8 V, VIH ≥ 2.0 V - Matches standard LS-TTL logic levels for seamless integration. |
| Output Type | Open-collector - Enables wired-AND bus arbitration, level shifting, and multi-drop configurations. |
| Operating Temp | 0°C to +70°C - Qualified for commercial-grade embedded and instrumentation applications. |
Pinout & Package
SN74LS644-1N3 is supplied in a 20-pin plastic DIP (dual in-line package) with 0.3-inch body width and standard through-hole mounting.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (G\) | Active-low Output Enable | Drives all outputs high-Z when HIGH; enables transceiver when LOW. |
| 2–9 (A1–A8) | Bus A Data Inputs/Outputs | Bi-directional terminals for first 8-bit bus; open-collector on output side. |
| 10 (GND) | Ground Reference | Common return path for logic and output current sinking. |
| 11–18 (B1–B8) | Bus B Data Inputs/Outputs | Bi-directional terminals for second 8-bit bus; open-collector on output side. |
| 19 (DIR) | Direction Control Input | HIGH enables A→B flow; LOW enables B→A flow. |
| 20 (VCC) | Positive Supply | 5-V nominal power rail; decoupling capacitor required at pin. |
Key Features
| Feature | Design Value |
|---|---|
| Octal bidirectional data path | Single chip replaces eight discrete transceivers, reducing board space and interconnect complexity. |
| Open-collector outputs | Enables wired-AND bus structures and interface to higher-voltage or mixed-logic systems via pull-up. |
| 48-mA sink capability (-1 version) | Eliminates need for external driver stages when interfacing to multiple TTL loads or LEDs. |
| Standard LS-TTL compatible inputs | Direct drop-in replacement for existing LS logic without level-shifting circuitry. |
Applications
| Industrial Backplane Interface | Legacy Printer Parallel Port |
|---|---|
Use Scenario: Isolating CPU address/data bus from peripheral expansion slots in programmable logic controllers. IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing data flow between master and slave modules under DIR-controlled arbitration. Use Value: Open-collector outputs prevent bus contention during hot-swap events and support daisy-chained interrupt lines. | Use Scenario: Connecting microcontroller-based print engine controller to Centronics-compatible parallel interface. IC Role / Device Role / Timing Role: Level-translating and current-boosting transceiver for STROBE, ACK, BUSY, and data lines. Use Value: 48-mA sink per line drives standard printer buffers and status LEDs without external drivers. |
| Test Equipment Bus Arbitration | EPROM Programming Adapter |
Use Scenario: Sharing a common test bus among multiple instrument modules in automated test systems. IC Role / Device Role / Timing Role: Wired-AND enabled bus isolator allowing multiple modules to assert shared control signals. Use Value: Open-collector outputs implement hardware OR logic for interrupt aggregation and status polling. | Use Scenario: Adapting 5-V microcontroller GPIOs to EPROM VPP programming voltage control and data latching. IC Role / Device Role / Timing Role: Direction-controlled data latch and high-current driver for EPROM address/data bus switching. Use Value: DIR signal toggles between address load and data write phases; 48-mA drive ensures reliable EPROM write pulse delivery. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LS245N | 3-state outputs (not open-collector); 24-mA IOL; non–-1 version | Lacks wired-AND capability; requires separate bus termination; lower drive strength | Select when 3-state isolation suffices and no wired-AND or high-current sinking is needed. |
| SN74LS644N | Same pinout and function but rated for 24-mA IOL (non–-1 version) | Lower output sink current limits use in LED-driving or multi-load scenarios | Select only if system loading stays within 24-mA per line and cost sensitivity outweighs performance margin. |
Compared with SN74LS644N and SN74LS245N, the SN74LS644-1N3 provides unique value in applications requiring both open-collector flexibility and 48-mA drive-enabling direct interface to legacy peripherals, status indicators, and wired-bus architectures without added components.
Availability
SN74LS644-1N3 is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy printer ports, test equipment bus arbitration, and EPROM programming adapters requiring stable component supply and long-term obsolescence management.
Supply support for SN74LS644-1N3 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Texas Instruments is a global semiconductor company founded in 1930, specializing in analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.
The SN74LS644-1N3 belongs to TI's legacy TTL logic product line, engineered specifically for robust, low-speed bidirectional bus interfacing in mission-critical industrial and instrumentation systems where reliability and long-term availability are essential.
FAQ
What is the maximum sink current per output for SN74LS644-1N3?
The SN74LS644-1N3 is rated for 48 mA maximum sink current (IOL) per open-collector output, as specified in the SDLS189 datasheet revision March 1988. This enhanced rating distinguishes the -1 version from the standard SN74LS644N (24 mA). Exceeding this limit risks parametric shift or long-term reliability degradation in the SN74LS644-1N3.
Does SN74LS644-1N3 support 3-state outputs?
No, the SN74LS644-1N3 features open-collector outputs-not 3-state. Its outputs can only sink current or float (high-impedance when disabled by G\); they cannot actively drive HIGH. This differs from devices like SN74LS245N. The SN74LS644-1N3 requires external pull-up resistors for HIGH-level logic assertion.
What is the function of the DIR pin on SN74LS644-1N3?
The DIR (direction control) pin on SN74LS644-1N3 determines data flow direction: when DIR = HIGH, data transfers from A-bus to B-bus; when DIR = LOW, data transfers from B-bus to A-bus. This single-pin control enables flexible bidirectional communication without external multiplexing logic in the SN74LS644-1N3.
Is SN74LS644-1N3 compatible with standard LS-TTL input thresholds?
Yes, SN74LS644-1N3 accepts standard LS-TTL input voltage levels: VIL ≤ 0.8 V (LOW) and VIH ≥ 2.0 V (HIGH). Its input structure matches LS-family specifications, ensuring interoperability with SN74LS00, SN74LS373, and other LS logic without level-shifting circuitry in the SN74LS644-1N3 design.
What package type is used for SN74LS644-1N3?
The SN74LS644-1N3 is packaged in a 20-pin plastic dual in-line package (PDIP) with 0.3-inch body width and through-hole mounting. This N-suffix package is industry-standard for legacy board assembly and prototyping, and is fully compatible with socketed implementations of the SN74LS644-1N3.
SN74LS644-1N3 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 20-DIP (0.300", 7.62mm)
- Packaging:
- Bulk
- Product Status:
- Active
- Logic Type:
- Transceiver, Inverting
- Number of Elements:
- 1
- Number of Bits per Element:
- 8
- Input Type:
- -
- Output Type:
- Open Collector
- Current - Output High, Low:
- 100µA, 24mA
- Voltage - Supply:
- 4.75V ~ 5.25V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 20-PDIP
SN74LS644-1N3 FAQ
1.How can I place an order for SN74LS644-1N3 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS644-1N3 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for SN74LS644-1N3 reliable?
The price and inventory of SN74LS644-1N3 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS644-1N3 is usually 5 days.
3.What payment methods are accepted for SN74LS644-1N3?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS644-1N3 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74LS644-1N3?
SN74LS644-1N3 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS644-1N3 order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for SN74LS644-1N3?
For technical support, including SN74LS644-1N3 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS644-1N3 requirements.
6.How does Aetrix verify that SN74LS644-1N3 is sourced from the original manufacturer or authorized distributors?
All SN74LS644-1N3 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that SN74LS644-1N3 meets industry standards.
7.What is the process for return or replacement of SN74LS644-1N3?
All SN74LS644-1N3 units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS644-1N3, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The SN74LS644-1N3 part is unused and in its original packaging.
Return procedure for SN74LS644-1N3:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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